1. Field of Invention
This invention relates generally to a baffle that fits onto the tube of a fluorescent lamp to assume the shape of an undulating shade that acts to diffuse the light emanating from the lamp and soften the illumination provided thereby as well as to absorb ambient sounds to reduce the noise in the room in which the lamp fixture is installed.
2. Status of Prior Art
A fluorescent lamp operates by converting ultraviolet energy into visible light. A fluorescent lamp is provided with a glass tube whose inner surface has a phosphor coating adapted to absorb radiant energy of a given wavelength and to reradiate it at a longer wavelength.
Contained in the glass tube are electrodes and a small amount of mercury. The electrodes provide a source of electrons to initiate an arc discharge which vaporizes the mercury to produce ultraviolet energy that excites the phosphors. A fluorescent lamp produces visible light at several times the efficiency of an incandescent bulb having a filament heated by current passing therethrough. Hence a 30 watt fluorescent lamp yields substantially more light than a 100 watt incandescent bulb.
However light generated by a fluorescent lamp lies mainly in the short wavelength portion of the visible light spectrum, whereas light emitted from an incandescent bulb lies mainly in the long wavelength portion. As a consequence of this distinction, though light from a fluorescent lamp is brighter than light from an incandescent bulb having the same wattage, the light emitted by the lamp is harsh and glaring, and therefore difficult on the eyes of those who are exposed to its rays.
Because of the drawback of fluorescent lamps, their use is largely confined to industrial and commercial applications that require high levels of illumination. Another reason why fluorescent lamps are not found in domestic and non-commercial environments except in kitchens, is that their appearance is strictly utilitarian and not usually acceptable for such environments.
Yet another factor militating against the use of fluorescent lamp fixtures is that ambient sounds impinging thereon are bounced, not absorbed thereby. This makes it difficult to fully acoustically insulate the room in which the fixtures are installed. Thus should the room ceiling in the regions thereof surrounding the fixtures be lined with acoustic tiles to absorb ambient sounds, the sounds will be enhanced by the sounds reflected from the fixtures. Hence the noise level in the room will remains high, particularly if several fluorescent light fixtures are installed therein.
Since the present invention deals with a baffle that fits onto the tube of a fluorescent lamp and acts as a light shade, of prior art interest are the following patents:
The patent to Curzon U.S. Pat. No. 2,595,771 (1952) shows a fluorescent tube on which is fitted a solid glass or plastic shade that runs the length of the tube. The 1961 Frantz U.S. Pat. No. 2,990,763 discloses a mercury vapor lamp for use in photographic printing onto which is fitted a row of horseshoe-shaped plates which act to collimate the light rays from the lamp. The 1964 patent to Long U.S. Pat. No. 3,140,055 fits an elongated U-shaped plastic shield onto a fluorescent lamp.
The patent to Peterson U.S. Pat. No. 4,122,511 (1978) is of interest because it considers the effect of attaching a shade onto a fluorescent lamp to reduce glare. Peterson who clamps a plastic shade onto the fluorescent tube, points out that prior art shades, though reducing glare, also sharply reduce the amount of light emanating from the lamp. The main advantage of the Peterson shade is that even though it reduces glare, it ensures utilization of at least 75% of the light emitted from the tubular lamp.
In the Lautzenheiser U.S. Pat. No. 5,490,467 (1995) a tubular lens is telescopically mounted over a fluorescent lamp to reduce glare. This lens is formed by prism-shaped triangular rings. In the 1993 Sugimoto U.S. Pat. No. 5,241,462, supported on a fluorescent tube on either side thereof is a wing composed of parallel, transparent prisms which act to disperse the light. In the to Suzuki U.S. Pat. No. 5,101,330 and Katoh U.S. Pat. No. 5,144,539, a fluorescent lamp is mounted on a reflecting plate whose reflected rays are projected through a diffusion plate.